Background and
Objective:
Studies have shown that alteration in photoperiod influences secretion of many
hormones. The aim of this study was to investigate the effect of different
periods of darkness on serum level of T3, T4 and TSH in male rats. Materials and
Methods:
In this experimental study, 30 male Wistar rats were randomly divided into
control group (exposed to 12 h light-12 h dark), and groups exposed to 13, 15,
21 or 21 h of darkness/day of 6 rats in each group. After 8 weeks, blood
samples were collected using cardiac puncture method and following serum
collection, the levels of T3, T4 and TSH were measured by radioimmunoassay. The
data were statistically analyzed using ANOVA. Results: Serum T3 and T4
levels did not significantly change in rats exposed to darkness for 13 and 15
h/day as compared to control animals however, significantly decreased in rats
exposed to darkness for 18 and 21 h/day (p < 0.05). Serum level of TSH did not
significantly change in experimental groups as compared to control animals. Conclusion: The findings suggest
that prolonged periods of artificial darkness at least up to 50% over the
standard scale can reduce thyroid activity and serum levels of thyroid hormone.
It is suggested that darkness can be considered as a probable factor in
hypothyroidism occurrence.
Ahmadi, R., Nargesi, S., & Amini, N. (2013). The effect of increased dark phase of photoperiodic cycle on serum level of T3, T4 and TSH in male rats. Daneshvar Medicine, 21(3), 63-68.
MLA
Rahim Ahmadi; Sanaz Nargesi; Noushin Amini. "The effect of increased dark phase of photoperiodic cycle on serum level of T3, T4 and TSH in male rats". Daneshvar Medicine, 21, 3, 2013, 63-68.
HARVARD
Ahmadi, R., Nargesi, S., Amini, N. (2013). 'The effect of increased dark phase of photoperiodic cycle on serum level of T3, T4 and TSH in male rats', Daneshvar Medicine, 21(3), pp. 63-68.
VANCOUVER
Ahmadi, R., Nargesi, S., Amini, N. The effect of increased dark phase of photoperiodic cycle on serum level of T3, T4 and TSH in male rats. Daneshvar Medicine, 2013; 21(3): 63-68.
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